A Backward Look at Scientific Instrumentation - Analytical Chemistry

A Backward Look at Scientific

Instrumentation John T. Stock Department of Chemistry University of Connecticut Storrs, CT 06269-3060

I well remember the time when we were told t h a t t h e b a l a n c e , b u r e t , and other volumetric glassware were the prospective chemist's best friends. In my London high school, we were t a u g h t to push m e a s u r i n g equipment to the limit. I recall two "zero-cost" experiments. We had to estimate, to the nearest 0.1 mL, the volumes of water contained in a se­ ries of 100-mL measuring cylinders. Then came the "weighing by swings" of s e p a r a t e small objects A and B, when we noted the sum of these two weights. Finally, we weighed A and Β together and learned t h a t , how­ ever good the balance, satisfactory agreement of the two totals required a self-consistent set of weights! In this REPORT I focus the development of various types of instrumentation, emphasizing the value of historical instruments as an important part of the scientist's heritage.

Balances My first encounter with balances oc­ curred when, as a small boy, I was t a k e n to t h e Science M u s e u m in London. I quickly passed by exhibits without buttons or handles to make things move. However, I recall being stopped by the collection of historic b a l a n c e s . I w a s i m p r e s s e d by t h e R a m s d e n "cone b e a m " i n s t r u m e n t shown in Figure 1. Later, I read that this balance had come into being at the behest of the tax collector—the British government needed accurate figures for the specific gravities of alcohol-water mixtures so t h a t the proper duty on "spirituous liquors" could be levied. Some four decades later, as Honorary Research Fellow, I reported on the m u s e u m ' s entire collection of balances (1).

Eventually, these studies were ex­ t e n d e d (2, 3). W h e n s e a r c h i n g for h i s t o r i c i n s t r u m e n t s , or even for facts about them, one often reaches an apparent dead end. This occurred while I was searching for t h e b a l ­ ances used to re-establish the Impe­ r i a l pound after t h e B r i t i s h s t a n ­ dards of weights and measures had been destroyed in a fire in 1834. I found t h e location of t h e s m a l l e s t balance and also learned of the fate of the mid-sized one (2). However, I could not trace the major instrument (4). William Hallowes Miller ( 1 8 0 1 80), who described the lengthy work of re-establishment, gave the follow­ ing account of this balance. These comparisons were made with a bal­ ance of extreme delicacy procured from Mr. Barrow. In its construction it nearly resembles the balances of the late Mr. T. C. Robinson. The beam is made suffi­ ciently strong to carry a kilogramme in each pan. The middle knife edge is about 1.93 inch long, and rests, when the bal­ ance is in action, throughout its whole length on a single plane surface of quartz. The surfaces of quartz which rest upon the extreme knife edges, and from wbich the pans are suspended, are also plane. The distance between the extreme knife edges is about 15.06, and the length of each about 1.05. . . . Despite n u m e r o u s inquiries and searches since 1965, this balance has not been found. This is doubly seri­ ous; not only is there a loss of a su­ perb example of instrument making, but also the balance was the means by which a national standard was re­ established. Despite the failure to achieve the main objective, the inquiries did en­ lighten me in other directions. I had not known t h a t Henry Barrow (1790-1870), who made the missing balance, was hired at the request of then Captain George Everest (17901866) as i n s t r u m e n t m a k e r for t h e Great Trigonometrical Survey of In­ dia (5).

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Like many others, I had regarded the so-called chainomatic balance as an American invention of 1916. In this type of balance, the adjustable drag of a fine chain is used to elimi­ n a t e t h e need for w e i g h t s smaller than 0.1 g. In fact, the principle had been described a q u a r t e r century earlier, a n d a "chain balance" was available in France before 1899 (6). Although r e q u i r i n g g r e a t care in design, construction, and adjust­ ment, the two-pan balance is essen­ tially a simple device and shows that a n i n s t r u m e n t does not have to be complicated to be valuable. An ex­ treme example is the surgeon's onepiece scalpel. Another is the blow­ pipe, which h a s a most i n t e r e s t i n g history (7). Between 1751 and 1863, no fewer than 11 elements were dis­ covered with t h e aid of this highly portable device. The buret, appear­ ing as a one-piece pour-type vessel nearly two centuries ago, acquired t h e vertical form with stopcock in 1846 (8). Given t h a t t h e i r l i t e r a r y o u t p u t w a s often l i m i t e d to b i l l s , t r a d e cards, and the like, the early instru­ m e n t m a k e r s t e n d to be forgotten. Their memorials lie in the discover­ ies made by the scientists who used t h e i n s t r u m e n t s . Such u s e r s often became expert glass workers; great mechanical ability was claimed less f r e q u e n t l y . C h a r l e s V e r n o n Boys (1855-1944) possessed such ability in t h e h i g h e s t degree. His profes­ sional career began at London's Royal School of M i n e s , w h e r e h e worked on an unusual technique for measuring electrolytic conductivity and t h e n on t h e production of ex­ tremely fine quartz torsion fibers (9). In 1798, Henry Cavendish ( 1 7 3 1 1810) determined the gravitational constant. He torsionally m e a s u r e d the attraction between massive lead balls and smaller ones hanging from t h e e n d s of a 6 - f o o t - l o n g b e a m . When Boys described his redetermi0003 - 2700/93/0365 -344A/$04.00/0 © 1993 American Chemical Society

nation of this constant in 1895, he used tiny gold balls suspended from a beam only 0.9 in. long. A n o t h e r striking application of Boys' mechanical ability was the "radio-micrometer," reportedly able to detect h e a t equivalent to that given off by a candle a mile away. Both of the Boys instruments as well as his fiber-making e q u i p m e n t a r e in t h e London Science Museum. When the coal-gas industry began in the early 1800s, its o u t p u t was used for o p e n - f l a m e l i g h t i n g . Accordingly, the quality of the gas was assessed by its illuminating power. Toward the end of the century, the use of gas spread to lighting by gas m a n t l e s (10) and h e a t i n g . E v e n t u ally, a declared calorific value of the gas b e c a m e a legal r e q u i r e m e n t . Boys became a gas referee in 1897 and developed the flow calorimeter, which became t h e official B r i t i s h test i n s t r u m e n t . He t h e n designed and built the extremely complicated recording gas calorimeter shown in Figure 2. However, Boys did not despise the simple; in Figure 3, he is shown with another interest—soap bubbles! Optical instrumentation The development of optical devices gave the i n s t r u m e n t m a k e r s a new problem. Often they depended on a subcontractor to provide lenses and other components. The first need for t h e m a k e r of optical devices w a s defect-free glasses of differing r e fractive indices. Composite lenses could then be made from these materials, so that the spherical and chromatic a b e r r a t i o n s associated with one-piece lenses could be minimized. This led to a considerable improvement in telescope lenses during the 18th c e n t u r y (11). Obviously, t h i s improvement passed to the design of optical instruments in general. F i g u r e 4 shows F r e n c h optician Charles Chevalier (1804-59) and

British physicist Charles Wheatstone (1804-75). Chevalier made lenses for Jules Duboscq (1817-86), inventor of a colorimeter widely used until well into the present century (12). Duboscq was a pioneer in stereoscopic a n d o t h e r p h o t o g r a p h y , and his existing daguerreotypes are highly regarded. Electrical instrumentation Progress in all fields of science often depends upon the availability of suitable electrical i n s t r u m e n t a t i o n , as described in a previous report (13). The development of methods for the m e a s u r e m e n t of electric c u r r e n t is

REPORT described in a Science M u s e u m monograph (14). The laying of t r a n s atlantic cables, begun in 1858, fostered the development of high-sensitivity galvanometers. Knowing t h a t telegraphic signals from across the A t l a n t i c were very weak, William Thomson ( 1 8 2 4 - 1 9 0 7 ) , l a t e r Lord Kelvin, realized t h a t h e needed a "frictionless p e n " to record on t h e traveling paper tape. In his "siphon recorder," patented in 1867, ink was fed to a fine glass tube mounted on the deflection coil, so t h a t the tip of the tube was j u s t clear of the tape. An applied potential between the tip and a plate beneath the tape caused the continuous ejection of ink in tiny

Figure 1. Ramsden balance, 1789. The pans and suspensions are missing. (Reproduced with permission of the Trustees of the Science Museum, London.)

drops (15). Thus, "ink-jet" printing is by no means new. The siphon recorder was, of course, merely a detector. The problem of the q u a n t i t a t i v e recording of very small voltages or currents was taken up by Hugh Longbourne Callendar (1863-1930). Figure 5 shows his recorder, p a t e n t e d in 1897, designed for platinum-resistance thermometry. A sensitive galvanometer exerts its control by energizing one or another of a pair of relays, according to the direction of the galvanometer deflection. The pen is then driven by clockwork across the chart, until a contact on a slidewire has returned the deflection to zero. Other examples of power-assisted small-signal recording are the "thread recorder," in which the freely moving pointer of the galvanometer is periodically depressed on an inked thread above the chart roll, and the Leeds and Northrup "Micromax" and earlier potentiometric recorders. In forms such as the steam-engine indicator, " X - Y " r e s p o n s e developed quite early in the engineering industry. The laboratory electrical X - Y r e c o r d e r owes i t s o r i g i n to h o m e w o r k s h o p a c t i v i t i e s in t h e period 1936 to 1938 (16). Mechanics and hydraulics Automation or mechanization in the fields of mechanics and hydraulics appeared more t h a n 1000 years ago. More recent examples are the 1728 p a t t e r n - w e a v i n g loom, which was controlled by punched cards, and the B o u l t o n - W a t t steam-engine governor of 1788. About 1880, examples of

Figure 3. Charles Vernon Boys. Figure 2. Recording gas calorimeter, 1922.

(Reproduced with permission of the Trustees of the Science Museum, London.)

ANALYTICAL CHEMISTRY, VOL. 65, NO. 7, APRIL 1, 1993 · 345 A

REPORT mechanization in the laboratory be­ gan to appear (17). These were sim­ ple devices to control heating by gas for a fixed time, or for evaporation to a p r e d e t e r m i n e d stage. S o m e w h a t more c o m p l i c a t e d w e r e a r r a n g e ­ ments for mechanizing the tedious washing of a gravimetric precipitate and for t h e r e p e t i t i v e r a i s i n g a n d lowering of m e r c u r y levels, which were needed in high-vacuum pump­ ing systems. Figure 6 shows an arrangement of the same period for the repeated agi­ tation of the gas-liquid interface in a selected absorption vessel of an Orsat gas analyzer. Water from A runs continuously into cylinder B. In this cylinder, a long test tube is placed over the central tube, the lower end of which is at E. Air pressure, caused by the rising water, is t r a n s m i t t e d from G through H, J, M, and Ν to the bottle on the right, so that the liquid level in the absorption vessel is de­ pressed. When the water level in the cylinder reaches D, the rapid siphon­ ing through the central tube relieves the pressure, thus restoring the level in the absorption vessel. The cycle then repeats. Widespread furnace operation made flue-gas carbon dioxide moni­ tors important industrial analytical instruments. (An account of the his­ tory of these devices h a s appeared [18]). The first patents were granted in G e r m a n y in 1893. For s e v e r a l y e a r s after t h i s , m a n u a l f l u e - g a s monitoring was still commonly prac­ ticed. By 1916, however, the use of

recording m o n i t o r s h a d become so widespread t h a t the U.S. Bureau of Mines issued an extensive bulletin on the performance of competing de­ vices. At t h a t time, some of the de­ vices involved q u i t e c o m p l i c a t e d glassware, as indicated in Figure 7. Some other examples of early in­ dustrial mechanization are the pro­ cessing of photographic, dyeing, or cooking operations; the dosing of wa­ ter to remove turbidity; and a frac­ t i o n a l d i s t i l l a t i o n i n s t a l l a t i o n of 1907, which relied on the a s s u m p ­ tion t h a t boiling point and density increase together (19). By the 1920s, the theory and practice of distillation had greatly developed; sophisticated column controls were then in use. Electrochemistry In 1873, Willoughby Smith ( 1 8 2 8 91) observed t h a t the electrical resis­ tance of a bar of selenium decreased when the bar was exposed to light. T h i s d i s c o v e r y led to t h e l i g h t sensitive selenium cells used in vari­ ous early devices. A picture telegra­ p h y a p p a r a t u s w a s d e s c r i b e d in 1881. A more practical example was the comparison photometer shown in Figure 8, which was reproduced from the 1907 patent (20). Selenium in the cell is rapidly oscillated between po­ sitions a and b. The distances of the l i g h t sources i a n d j a r e t h e n a d ­ justed so t h a t the signal of the detec­ tor, a m e t e r or telephone receiver, remains unchanged. A more striking application used the selenium cell in a complicated

mechanization of water softening by the lime-soda process (21). This ap­ p a r a t u s sampled the treated water, added reagents such as phenolphthalein, photoscopically a s s e s s e d t h e state of the sample, adjusted the dos­ ing with the softening agents if nec­ essary and, finally, emptied the sam­ pling vessel. A paper published in 1923, when alkali-metal photoelectric cells had become available, commented t h a t only a few industrial applications of l i g h t - s e n s i t i v e cells h a d been pro­ posed (22). Typical applications were for counting, control of liquid level and, more ambitious, optical Marshtesting for arsenic, a catalyst poison in burner gases involved in the pro­ duction of sulfuric acid. In 1776, Cavendish made the first quantitative comparisons of electro­ lytic conductivity. His only "indica­ tor" was the highly subjective experi­ ence of electric shock! Much l a t e r came d e v e l o p m e n t s such as h i g h precision absolute m e a s u r e m e n t s , conductometric titrimetry, and conductometric monitoring (23).'Moni­ toring t h a t uses the marked change in conductivity caused by the pres­ ence of very low c o n c e n t r a t i o n s of electrolytes is crucial for the assess­ m e n t of t h e q u a l i t y of distilled or demineralized water. On the other hand, modern industrial electrodeless instrumentation can handle ma­ terials such as hot sodium hydroxide solution, oleum, and raw sewage. The N e r n s t equation, formulated in 1889, is a cornerstone of electro­ chemistry. One of Walther Nernst's

Figure 5. Callendar recorder, 1897. Figure 4. Charles Chevalier (left) and Charles Wheatstone, ca. 1843. 346 A · ANALYTICAL CHEMISTRY, VOL. 65, NO. 7, APRIL 1, 1993

(Reproduced with permission of the Trustees of the Science Museum, London.)

REPORT colleagues at Leipzig was Robert Behrend ( 1 8 5 6 - 1 9 2 6 ) , who eventually p u b l i s h e d a b o u t 100 p a p e r s (24). With one remarkable exception, essentially all of these concerned organic chemistry. The exception was his 1893 account, in which he described the application of N e r n s t ' s work to the measurement of the solubilities of sparingly soluble mercurous salts. Behrend realized that his technique could be used to follow the course of precipitation reactions; he described the first potentiometric titrations, those of halides with silver nitrate solution. Recent collaborative reports have discussed the choice of the hydrogen electrode as the base for the electromotive series, and the development

Figure 6. Partially mechanized gas analyzer, 1880.

Figure 7. Interior of Sarco carbon dioxide monitor, 1907.

of t h e pH m e t e r a n d t h e glass pH electrode (25). By 1909, Haber and Klemensiewicz h a d developed t h e glass electrode a n d h a d used it in potentiometric acid-base titrimetry. Because of the high electrical resist a n c e of t h e g l a s s m e m b r a n e , obs e r v a t i o n s h a d to be m a d e w i t h a quadrant electrometer. The transformation of the glass electrode from a specialized item into a routine pHmeasuring device had to await develo p m e n t s in electronics. In t h e interim, pH measurements were made eolorimetrically or, by use of electrode systems of low electrical resistance, potentiometrically. Although the hydrogen electrode meets this electrical requirement, it needs a supply of hydrogen and is susceptible to deactivation by "poisoning." Nevertheless, this electrode w a s u s e d in i n d u s t r y (26). In r e sponse to the deactivation problem, a robust electrode system with easily replaceable platinum elements was patented in 1923. The system, which i n c o r p o r a t e d a calomel r e f e r e n c e electrode, was used in a scheme that permitted the recording of the pH of a flowing stream and governed the making of additions to keep the pH constant. A l t h o u g h l i m i t e d to s a m p l e s in which the pH was less than about 8, the simplicity of the platinum-quinhydrone electrode made it a widely u s e d a l t e r n a t i v e to t h e h y d r o g e n electrode in t h e period before t h e general advent of the glass electrode (27). Successful attempts were made

to record the pH of flowing streams by continuous dosing with a solution of quinhydrone. When pH measurements accurate to within 0.1-0.2 units are acceptable, the a n t i m o n y - a n t i m o n y oxide electrode, another low-resistance device, can be used with the added advantages of robustness and simplicity. Figure 9 shows a typical antimony-calomel unit of the early 1930s. T h e i n d i c a t o r e l e c t r o d e is simply elemental antimony, which acquires its oxide coating during use. By the late 1930s, industrial users of the antimony electrode numbered in the hundreds. At a symposium held in Atlanta in the spring of 1991 to mark the bicentenary of the birth of Michael Faraday (1791-1868), one of the papers outlined the pathway leading from the report of the electrolysis of water in 1800 to t h e e n u n c i a t i o n of t h e laws of electrolysis in 1834 (28). To determine the total amount of electricity used in an experiment, Faraday devised several forms of the volt a m e t e r , b a s e d on t h e g a s o m e t r i c measurement of the products of the electrolysis of water. These procedures were studied by other workers, who m a d e i n c r e a s i n g l y a c c u r a t e measurements of the electrochemical equivalent of water (29). Believing t h a t m e t a l deposition from aqueous solution was a secondary process, Faraday sought quantitative data from the much more difficult electrolysis of fused salts. The crystalline n a t u r e of the deposited silver gave problems when he tried fused silver chloride. A few months after F a r a d a y ' s 1834 p u b l i c a t i o n ,

Figure 8. Selenium cell comparison photometer, 1907.

Figure 9. Industrial antimony-calomel pH electrode system, ca. 1930.

348 A · ANALYTICAL CHEMISTRY, VOL. 65, NO. 7, APRIL 1, 1993

Carlo Matteucci (1811-68) described the (aqueous) silver-deposition volt a m e t e r . As a n a d d e d i r o n y , t h e F a r a d a y c o n s t a n t , now k n o w n to w i t h i n a few p a r t s per million, is based on the silver voltameter. Nobel Laureate Theodore William Richards ( 1 8 6 8 - 1 9 2 8 ) was one of t h e m a n y who successively improved the precision of the silver voltameter (30). In 1902 he suggested that the anachronistic term, voltameter, should be replaced by the descriptive term, coulometer. During the period 1908-47, the ampere was internationally defined in terms of the rate of deposition of silver from aqueous silver nitrate solution. Various other chemical and electromechanical coulometers came into use, followed by electronic coulometers. Two major areas of electrolysis do not require the a t t a i n m e n t of 100% c u r r e n t efficiency, however d e s i r able. The first is electropreparation, described in t h e v a s t l i t e r a t u r e of laboratory organic syntheses (31-33). S o m e of t h e s e s y n t h e s e s h a v e reached i n d u s t r i a l scale. The m a s sive production of aluminum, sodium hydroxide, and chlorine are examples of inorganic a p p l i c a t i o n s (34). Intense hardness, which may hinder or prevent the use of conventional tools, does not affect e l e c t r o m a c h i n i n g , which involves selective anodic destruction of the metal to be shaped or drilled (35). The other area is electrogravimetry, at one time a major technique for the determination of certain metals. On the basis of his short paper of 1864, Oliver Wolcott Gibbs ( 1 8 2 2 1908) is usually named as the originator of this technique. However, the German railway chemist, C. Luckow, claimed to h a v e been u s i n g t h e method since 1860. It is likely t h a t t h i s claim w a s well founded; certainly Luckow, and not Gibbs, went on to develop the technique (36). By changing conditions such as pH, it is sometimes possible to analyze mixtures by successive deposition. A notable advance in both the preparative and the analytical aspects of electrolysis came from the realization t h a t selectivity depends largely on control of t h e p o t e n t i a l of t h e working electrode. Henry Julius Sand (1873-1944), known mainly for the chronopotentiometric equation t h a t bears his name, was a leading exponent of i n t e r n a l - e l e c t r o l y s i s , controlled-potential, and microchemical electrogravimetry (37). The use of controlled cathode potential by Fritz Haber (1868-1934) made possible the elucidation of the

reaction stages in the electroreduction of n i t r o b e n z e n e (38). He, like Sand and others, had to control the potential manually; the potentiostat did not appear until 1942. The i n t r o d u c t i o n of t h e electric light bulb brought forth the problem of a s s e s s i n g a customer's usage of t h e dc electricity t h e n being s u p plied. Thomas Alva Edison ( 1 8 4 7 1931) did this by passing a known fraction of the current through amalgamated zinc electrodes immersed in zinc sulfate solution. Periodically, the anode was reweighed to assess the cost (39). In 1882, Edison used this principle in a meter incorporating a balance beam, the periodic tilting of which operated a mechanical counter. In response to the increasing use of commercial electricity, v a r i o u s other electrolytic m e t e r s appeared. Typical is a prepayment meter. Copper electrodes in copper sulfate solution are used; the anode hangs from the r i g h t - h a n d end of t h e balance beam, which operates a mercury switch t h a t is normally in the open position. Coins inserted in the meter are guided into t h e larger bucket, causing the beam to tilt, the switch to close, and the electrolysis to begin. E v e n t u a l l y , t h e decrease in anode weight allows the beam to return to its original position; the supply is interrupted until a further payment is made. Although attempts were made to r e t a i n electrolytic m e t e r s when power supplies changed from dc to ac, they were eventually supplanted by electromechanical instruments. The determination of quantities of electricity by measuring the products of electrolysis began with Faraday. A typical reverse approach, coulometric titration, involving the quantitative generation of a t i t r a n t by a known

Figure 10. Continuous coulometric recorder, 1948. (Reproduced from Reference 45.)

quantity of electricity, was not described until 1938 (40). The intervention of World War II probably delayed developments, but eventually coulometric titration at constant curr e n t b e c a m e a widely u s e d t e c h nique. A great advantage is simplicity. N e i t h e r p o t e n t i o s t a t nor coulometer is needed; the measured variable is merely that of time. The massive l i t e r a t u r e on coulom e t r i c t i t r a t i o n (41, 42) c o n t a i n s m a n y e x a m p l e s of a u t o m a t i o n or mechanization (43, 44). Apparently, t h e first example (not a c o n s t a n t current device) was t h a t shown diagrammatically in Figure 10. This titrator was originally designed during World War II for the continuous bromometric determination of mustard gas in air (45). Developed later as an i n d u s t r i a l i n s t r u m e n t , the t i t r a t o r found other uses, such as monitoring mercaptan odorants in town gas supp l i e s . T h e c o n t a m i n a t e d a i r is p u m p e d into t h e c e n t r a l c o m p a r t m e n t , c a u s i n g t h e sulfuric a c i d potassium bromide electrolyte solution to circulate. Negative feedback controls the rate of generation of bromine so t h a t a very slight excess is maintained in the cell. The determination of acids in chloride medium was one of the earliest coulometric t i t r a t i o n s (40). A platinum cathode and a silver anode were used, and an added pH indicator solution provided visual end-point detection. This type of technique is obviously inapplicable in the presence of any substance more easily reduced

Figure 11. Aston mass spectrograph, 1919. (Reproduced with permission of the Trustees of the Science Museum, London.)

ANALYTICAL CHEMISTRY, VOL. 65, NO. 7, APRIL 1, 1993 · 349 A

REPORT t h a n hydrogen ions or water. This difficulty was overcome by external t i t r a n t generation. In 1951, this approach w a s u s e d in a m e c h a n i z e d constant-current acid-base titrator. The value of historic instruments Compared with most modern equipment, the devices that have been described are generally simple. However, i n s t r u m e n t a t i o n experts, like o t h e r p r o g r e s s i v e s , s t a n d on t h e s h o u l d e r s of t h e i r p r e d e c e s s o r s . Some y e a r s ago, I pointed out t h a t historic i n s t r u m e n t s are an endangered species (46). It is easy to cannibalize or to jettison a n obsolescent instrument. This may not matter unless t h e i n s t r u m e n t in question is unique or is the last of its kind. Although plentiful in their day, early examples of carbon dioxide monitors or process controllers (47) are now rarely encountered. Aston's first mass spectrograph (Figure 11) is obviously unique. We are still making unique instruments—the prototypes on w h i c h p r o d u c t i o n m o d e l s a r e based! A damaged or even incomplete historic i n s t r u m e n t can sometimes be restored. Apart from the experts in

(5) Stock, J. T. Bull. Sci. lustrum. Soc. 1986 (9) 11—12 (6) Stock,' J. T. Bull. Hist. Chem. 1990(8), 12-15. (7 ) Jensen, W. B. In The History and Preservation of Chemical Instrumentation; Stock, J. T.; Orna, M. V., Eds.; Reidel: Boston, 1986; pp. 123-49, 244. (8) Szabadvary, F. History of Analytical Chemistry; Pergamon: New York, 1966; p. 236. (9) Stock, J. T. Bull. Sci. Instrum. Soc. 1989 (23), 2-6. (10) Stock, J. T.J. Chem. Educ. 1991, 68, 801-03. (11) Jaecks, D. H. In The History and Preservation of Chemical Instrumentation; Stock, J. T.; Orna, M.V., Eds.; Reidel: Boston, 1986; pp. 51-65, 244. (12) Stock, J. T. submitted. (13) Stock, J. T. Anal. Chem. 1980, 52, 1518 A-1523 A. (14) Stock, J. T.; Vaughan, D. The DevelThis work was partially carried out under the opment of Instruments to Measure Electric Research Fellowship Program of the Science Current; Science Museum: London, 1983. Museum, London. (15) Green, D.; Lloyd, J. T. Kelvin's Instruments and the Kelvin Museum; The University: Glasgow, 1970; p. 34. References (16) Moseley, F. L. Presented at the 178th National Meeting of the Ameri(1) Stock, J. T. Development of the Chemical can Chemical Society, Washington, DC, Balance; Science Museum: London, Sept. 1979; paper 11. 1969; p. 13. (17) Stock, J. T. Educ. Chem. 1983, 20, (2) Stock, J. T. /. Chem. Educ. 1968, 45, 7-10. 254-57. (18) Stock, J. T. Trends Anal. Chem. 1983, (3) Stock, J. T. Anal. Chem. 1973, 45, 2(1), 14-17. 974 A-980 A. (4) Stock, J. T. In The History and Preserva- (19) Stock, J. T. Amer. Lab. 1984, 16(6), tion of Chemical Instrumentation; Stock, 14-21. J. T.; Orna, M. V., Eds.; Reidel: Boston, (20) Bumb, H. German Patent 191,075, 1986; p. 244. 1907. museum workshops, there are specialists w h o s e r e s t o r a t i v e skill is matched by the respect they have for i n s t r u m e n t s on w h i c h t h e y work (48). The great museums of the world are much more t h a n mere exhibitors. They guard the scientific heritage of our successors, t h e y e d u c a t e , and they are centers of research. On my regular visits to the London Science Museum, I am always amazed by the numbers of school parties of all ages t h a t arrive daily. Perhaps, as I did, these visitors begin with a little "handle-turning." But they soon pass on to a realization of what we owe to science and technology!

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(21) Stock, J. T. Trends Anal. Chem. 1983, 2(11), 261-62. (22) Logan, L. Ind. Eng. Chem. 1923, 15, 40-43. (23) Stock, J. T. Anal. Chem. 1984, 56, 561 A—565 A (24) Stock, J. T. /. Chem. Educ. 1992, 69, 197-99. (25) Jas'elskis, B.; Moore, C. E.; Von Smolinski, A. In Electrochemistry, Past and Present; Stock, J. T.; Orna, M. V., Eds.; ACS Symposium Series No. 390; American Chemical Society: Washing­ ton, DC, 1989; Chapters 9, 18, and 19. (26) Stock, J. T. Bull. Hist. Chem. 1991 (10), 31-34. (27) Stock, J. T.J. Chem. Educ. 1989, 66, 910-12. (28) Stock, J. T. Bull. Hist. Chem. 1991 (11), 86-92. (29) Stock, J. T. /. Chem. Educ, in press. (30) Stock, J. T.J. Chem. Educ. 1992, 69, 949-52. (31) Fichter, F. Organische Elektrochemie; Steinkopff: Dresden, 1942. (32) Allen, M. J. Organic Electrode Pro­ cesses; Chapman & Hall: London, 1958. (33) Baizer, M. M. In Electrochemistry, Past and Present; Stock, J. T.; Orna, M. V., Eds.; ACS Symposium Series No. 390; American Chemical Society: Washing­ ton, DC, 1989; Chapter 13. (34) Leddy, J. J. In Electrochemistry, Past and Present; Stock, J. T.; Orna, M. V., Eds.; ACS Symposium Series No. 390; American Chemical Society: Washing­ ton, DC, 1989; Chapter 33. (35) McGeough, J. Α.; Barker, M. B. In Electrochemistry, Past and Present;

Stock, J. T.; Orna, M. V., Eds.; ACS Symposium Series No. 390; American Chemical Society: Washington, DC, 1989; Chapter 39. (36) Stock, J. T. Bull. Hist. Chem. 1990(7), 17-19. (37) Stock, J. T. In Electrochemistry, Past and Present; Stock, J. T.; Orna, M. V., Eds.; ACS Symposium Series No. 390; American Chemical Society: Washing­ ton, DC, 1989; Chapter 32. (38) Stock, J. T. / Chem. Educ. 1988, 65, 337-38. (39) Stock, J. T. /. Chem. Educ. 1989, 66, 417-19. (40) Ewing, G. W. In Electrochemistry, Past and Present; Stock, J. T.; Orna, M. V., Eds.; ACS Symposium Series No. 390; American Chemical Society: Washing­ ton, DC, 1989; Chapter 27. (41) Lingane, J. J. Electroanalytical Chem­ istry, 2nd éd.; Interscience: New York, 1958; Chapters 20, 21. (42) Stock, J. T. Anal. Chem. 1984, 56,

John T. Stock is emeritus professor of chemistry at the University of Connecti­ cut. Born in England, he received the Ph.D. and D.Sc. from the University of London. After extensive industrial and ac­ ademic experience he joined the faculty of the University of Connecticut in 1956. As an analytical chemist, he has been a longterm contributor to ANALYTICAL CHEMISTRY, both in the A pages and in -ι ρ η τ> the biennial reviews. His interest in the (43) Stock, J. T. Trends Anal. Chem. 1981, design, construction, and history of scien­ 1(3), 59-62. (44) Stock, J. T. Trends Anal. Chem. 1982, tific instruments, aroused in his youth, has developed throughout his life. He or­ 1(5), 117-20. (45) Shaffer, P. Α.; Briglio, Α.; Brockman, ganized the ACS symposia on the history J. A. Anal. Chem. 1948, 20, 1008-14. of chemical instrumentation in 1979 and (46) Stock, J. T. Chem. Eng. News 1979, 1985, and on the history of electrochem­ 57(31), 30. istry in 1988. He received the University (47) Stock, J. T. Trans. Newcomen Soc. 1987—88 59 15—29 of Connecticut Alumni Award for excel­ (48) Read,' W.'J. In The History and Preser­ lence in teaching in 1977 and the Dexter vation of Chemical Instrumentation; Stock, Award for outstanding contributions to J. T.; Orna, M. V., Eds.; Reidel: Boston, the history of chemistry in 1992. 1986; pp. 157-62.

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